Co and Ce Cation Impact on PEM Fuel Cell Performance

Abstract

PtCo/C is often used in the cathode in proton exchange membrane fuel cells to enhance performance. However, Co2+ cations can be released from the catalyst into the ionomer during operation. Additionally, Ce3+ cations are often introduced into the membrane as a chemical stabilizer. These cations replace protons of the ionomer acid cites and can redistribute during operation, resulting in local proton deficiencies, especially, in the cathode at high current densities [1-2]. While studies have shown severe performance loss due to Co2+ migration [3-4], the simultaneous impact of both Co2+ and Ce3+ has not been reported. Moreover, state-of-the-art cathodes often use high-surface-area carbon (HSC) with numerous PtCo particles within carbon internal pores. In absence of ionomer within these internal pores, it is unclear how the cations affect the proton activity and hence fuel cell performance. In this study, we performed controlled experiments where known amounts of Co and Ce cations were exchanged into the membranes and investigated the effect of cation concentration at different operating conditions. We also include the comparison of cation impact on electrodes with Vulcan and HSC supported cathode catalysts. Impedance spectroscopy was used to study the effect of cations on membrane and electrode proton resistances. The experimental results provide direct assessment of the cation impact on the fuel cell performance, and will also be used to improve our fuel cell performance model and provide direction for future fuel cell development. This work was partially supported by the US Department of Energy, Office of Energy Efficiency and Renewable Energy under grant DE-EE0007271. References T. A. Greszler, T. E. Moylan and H. A. Gasteiger, Chapter 49, Handbook of Fuel Cells – Fundamentals, Technology and Applications. Edited by Wolf Vielstich, Harumi Yokokawa, Hubert A. Gasteriger. Volume 6: Advances in Electrocatalysis, Materials, diagnostics and Durability. 2009 John Wiley & Sons, Ltd. Y. Cai, J. M. Ziegelbauer, A. M. Baker, W. Gu, R. S. Kukreja, A. Kongkanand, M. F. Mathias, R. Mukundan, and R. L. Borup, J. Electrochem. Soc., 165, F3132–F3138 (2018)S. Chen, H. A. Gasteiger, K. Hayakawa, T. Tada and Y. Shao-Horn, J. Electrochem. Soc., 157, A82 (2010).T. Okada, H. Satou, M. Okuno and M. Yuasa, J. Phys. Chem. B, 106 1267 (2002)Y. Cai, A. Kongkanand, W. Gu and T. E. Moylan, ECS Trans., 69, 1047 (2015).